Varnish resins and process of making same



Patented Nov. 22, 1938 UNITED STATES VARNISH RESINS AND PROCESS OF MAK-ING SALIE Carleton Ellis, Montclair, N. J., assignor to Ellis- FosterCompany, a corporation of New Jersey No Drawing. Application November15, 1934, Serial No. 753,123

3 Claims.

This invention relates to the production of phenolic resinous bodies bythe reaction of formaldehyde, or other active methylene containingbodies, with xylenols. Furthermore this inven- 5 tion teaches the methodof production of such resinous bodies in order that they may besubstantially oil-soluble, that is, soluble in drying or semi-dryingoils. In this class are included tung oil, linseed oil, perilla' oil,and soy bean oil.

This is a continuation in part based on my application Serial 751.867,filed November 24, 1924 Patent No. 1,980,987, Serial 578,219, filedNovember 30, 1931, Patent No. 2,089,828, and Serial 641,282, filedNovember 4, 1932 Patent No. 2,087,853. In my application Serial 751,867,

. there is described the making of xylenol-formaldehyde resins which maybe dissolved in a solvent and the solution mixed with fillers to producemolding compositions. In Serial 578,219, use is made of xylenol-aldehyderesins and xylenol-aldehyde resins modified with acetone as ingredientsfor oil varnishes. In Serial 641,232, oil-soluble xylenol-formaldehyderesins are prepared which may be dissolved in drying oils. The presentapplication deals with changes in the process for makingxylenol-formaldehyde resins and also methods of forming variousmodifications of the same, which modified resins are also oil-soluble.

The xylenols used in the present invention were commercial fractionswhich contain all six of the isomeric xylenols in various proportionsalong with smaller quantities of other phenolic bodies which are higheror lower homologues, or derivatives. In the following this complexmixture of xylenols will be termed mixed xylenols. Chemically theindividual xylenols differ vastly in their reactivity with aldehydes.Thus, the xylenol known as 1.3.5.xylenol (symmetrical xylenol) is themost reactive. This is because symmetrical xylenol has a maximum numberof vulnerable points at which formaldehyde combines (positions ortho orp'arato the phenolic group). The least reactive xylenol is the 45 1)(2,4) xylenol (or perhaps. (1). (2,6) xylenol) which has only onereactive position open. Thus, when a resin is formed by reacting, say, 1mole of formaldehyde with 1 mole of mixed xylenols, the most reactivexylenols tend to combine with a maximum amount of formaldehyde and passbeyond the stage of being readily oil-soluble. At the same time the lessreactive xylenols combine only partially or not at all and are largelyin a freeform at the end of thereaction. Consequently, when the mixedxylenols are treated with enough formaldehyde normally to form a resin,the resulting product is a mixture of resin and unreacted xylenols.Removal of the unreacted xylenols leaves ahard resinthat has so great atendency to heat-harden that it cannot be used in oil varnishes. Byproper proportioning of the formaldehyde it is possible to produce anoil-soluble resin; that is, by reacting the mixed xylenols with onlyenough formaldehyde to react with the more reactive constituents of 10the mixture to form an oil-soluble resin. The unreacted xylenols arethen removed and resinifled in a second step as hereinafter described.Aldehydes other than formaldehyde may be used to react with the reactivexylenols. I

In the present invention I propose to react mixed xylenols withformaldehyde in the proportions of about one mole of xylenols toone-half mole of formaldehyde, with or without a catalyst. The xylenolswhich thus react are hereinafter 20 referred to as more reactivexylenols; while the xylenols which do not react under these conditionsare hereinafter referred to as less reactive xylenols." The resinmixture so produced is blown with steam and the unreacted xylenols g5recovered from the condensed steam are still further reacted withformaldehyde in the presence, preferably, of an acid catalyst to producean oilsoluble resin. The resins produced in these two steps may be fusedtogether. In this way a com- 30 plete utilization of all the xylenols iseffected.

After steam distillation the xylenols. recovered have been found to beuniformly reactive; that is, they all have approximately the samereaction speed with formaldehyde. Since this is true they may beresinifled with normal amounts of aldehyde. Acid catalysts such ashydrochloric acid, sulphuric acid, o-phosphoric acid, acetic acid, andoxalic acid may be used to hasten the reaction. Furthermore, the methodsof reaction described in the above mentioned applications may be usedand the unreacted xylenols, recovered after steam blowing, used withacid catalysts after the methods of the present invention.

In some cases an alkaline catalyst is preferred. For instance, I mayreact mixed xylenols or the recovered xylenols referred to above withacetone in the presence of a strong acid. This reaction tends to producedihydroxydixylyldimethylmethane. This is then further reacted withformaldehyde in the presence of ammonium hydroxide. Light-colored,drying oil-soluble resins are thus obtained using small to large amountsof ammonia.

It may be noted here that the resins obtained 68 by reacting mixedxylenols with formaldehyde are in general fairly light-colored. Onexposure to the air they have a tendency to darken and as zinc dust,powdered aluminum, or bronze powder, 9. distinct bleaching action takesplace rendering the resins still more air and light stable. The resinsmay also be dissolved in a suitable solvent and reacted with. the metalpowder at the boiling point of the solvent.

The following examples are given to illustrate the methods set forthabove.

Example 1.2 parts of commercial mixed xylenols (boiling range 210-225C.) are refluxed with 1 part of 37% aqueous formaldehyde (1 mole ofxylenols to 0.75 mole of formaldehyde) for about 2 hours, or until awell-defined liquid resinlayer appears at the bottom of the reactionvessel. The temperature is then taken to C. and the water distilled off.After the resin has thus been substantially dehydrated, the temperatureis taken to 150 C. and the mass is blown with superheated steam. Thevapors are condensed and the unreacted phenolic bodies which distil overwith the steam are recovered. When these unreacted bodies no longer comeover, the distillation is stopped. The unreacted bodies, amounting toabout 0.6 part by weight, are collected and reacted in the proportion of1 mole recovered xylenols to 1 mole of formaldehyde in the presence of 1per cent of hydrochloric acid. This latter reaction proceeds ratherrapidly and when a well-defined resin layer appears at the bottom of thereaction vessel the reaction is stopped. The temperature is raised to110 C. and the water distilled off. When this latter resin has beendehydrated and steam-distilled to remove acrid bodies, it is mixed withthe resin from the first step and fused. The temperature may be taken toabout 200 C. When cooled to room temperature the final resin islight-colored, hard and brittle. It possesses little or no odor and isreadily soluble in tung oil.

In the first step of the operation as described above, no catalyst isused. However, by cutting down on the amount of formaldehyde fasterreaction is secured with an acid catalyst. By using less formaldehydethe resin which forms remains dissolved in the excess unreactedxylenols, giving a homogeneous viscous product. The unreacted xylenolsare then removed by steam distillation.

Example 2.--3 parts of commercial xylenols (boiling range 210-225 C.)are mixed with 1 part of 37 per cent aqueous formaldehyde and l per centof concentrated hydrochloric acid and boiled in a vessel fitted with areflux condenser for about one hour, or until a well-defined layer isformed at the bottom of the reaction flask. The temperature is taken to110 C. and the water distilled. After the: resin hasbeen dehydrated itis blown with steam and the recovered, unreacted xylenols (about 1%parts) heated with formaldehyde as in Example 1.

Example -3.5 parts of commercial xylenols (boiling range 205-220 C.) aremixed with 1 part of 37 per cent aqueous formaldehyde and 0.2 per centof oxalic acid. Refluxing is allowed to take place for about 2 hours.The liquid product is then dehydrated by distilling off the water at 110C. and is then blown with steam. The unreacted xylenols recovered fromthe condensed steam are then reacted with formaldehyde in the sameproportions as the first step of Example 1 with the exception that 3 percent of oxalic acid is used to catalyze the reaction. The resin fromthis second step is dehydrated by heating it to about C. and the resinfrom the first step, that from the second step and 1 per cent of zincdust are fused together at a temperature of 200 C. When cooled to roomtemperature, the resin is light in color, hard and brittle. It possesseslittle or no odor and is readily soluble in tung oil to form alight-colored, quick-drying varnish base.

Commercial mixed xylenols, or crude cresylic acid, may be reacted witheven less formaldehyde than used in the above example, the resindehydrated, then the excess xylenols removed by distillation atatmospheric pressure or under reduced pressures, as shown below.

Example 4.-10 parts of commercial mixed xylenols are mixed with 1 partof 37 per cent aqueous formaldehyde and 0.1 part of ortho-phosphoricacid and refluxed for 2 hours. At the end of this time the water isdistilled off and the liquid mixture distilled at atmospheric pressure.The temperature is finally taken to 240 C. The residue left in thedistilling flask is a hard, brittle, asphalt-like resin. This resin isreadily soluble in all the drying oils. The recovered xylenols may beresinified with formaldehyde according to the procedures of the previousexamples.

Besides making an oil-soluble resin according to the above method, I mayreact commercial mixed xylenols, or recovered unreacted xylenols, withvarying amounts of tung oil before resinifying with an aldehyde. In thisway what appears to be a chemical combination is secured between thedrying oil and phenolic resin. These products dry less rapidly thanvarnishes made by dissolving xylenol-aldehyde resins in a drying oil.

The amount of drying oil combined may be varied,

depending on the type and hardness of the resin desired.

Example 5.--2 parts of raw tung oil, 1 part of mixed commercial, orrecovered, xylenols and 4 per cent of ortho-phosphoric acid (based onthe xylenols) are heated together in a vessel fitted with an air-refluxcondenser to a temperature of about C. for 1 to 4 hours. The reactionproduct is then mixed with 0.6 part of 37 per cent aqueous formaldehydeand refluxing is continued with a water-cooled condenser for- 2 hours.At the end of this time the water is distilled off and the temperaturetaken to 260-270 C. in order to body the product to the desiredconsistency.

Example 6.-3 parts of raw tung oil, 1 part of mixed commercial (orrecovered) xylenols and 4 per cent of ortho-phosphoric acid are mixedand heated in a kettle provided with a reflux condenser for 2 hours at180 C. This reaction product is then washed free of acid with slightlyalkaline water. 600 grams of 37 per cent aqueous formaldehyde andsuflicient 25 per cent aqueous ammonia to form hexamethylenetetramineare added to the reaction product. Refluxing is allowed to take placefor 2 hours, then the product dehydrated and the temperature carried to260- 270 C. to body the varnish base to the desired consistency.

When mixed commercial xylenols are resinifled with formaldehyde in thepresence of a basic catalyst such as caustic soda, potassium hydroxideor carbonate, the reaction often becomes unmanageably violent with atendency to produce heat-hardening products which are, in general,insoluble in drying oils. The recovered xylenols from the abovedescribed two-step process are more evenly reactive and may beresinified in the presence of a basic catalyst. When using a basiccatalyst, I prefer to subsequently flux the resinous product obtainedwith rosin or ester gum to secure complete oil-solubility.

During the drying of a varnish film containing an unmodifiedphenol-aldehyde there is usually a tendency for the development of ayellow coloration even when the varnish itself is light in color.Fluxing a completely oil-soluble xylenol resin with a small amount ofrosin or a rosin ester considerably lightens the color of the driedvarnish film. It is to be understood that this fiuxing with rosin, orrosin ester, is in no way connected with the oil-solubility, but thatthe rosin merely servesas an agent which reduces after-'- yellowing ofthe varnish film. In place of rosin there may be used the various othernatural and fossil resins and their esters. A modicum of such resinswill usually serve the purpose, amounts ranging from 10 per cent to 30per cent. Lactic acid has a similar effect. Furthermore, thisafter-yellowing may be prevented by irradiating the varnish film orvarnish with ultra-violet light or natural sunlight. Another convenientmethod of producing a pale varnish film is to acylate the xylenol resinbefore dissolving the resin in the drying oil. For example, axylenolformaldehyde resin can be dissolved in aqueous sodium hydroxide.Gradual addition of benzoyl chloride causes the precipitation of alightbrown powder. A varnish made from the henzoylated resin and tungoil dries pale colored with no after-yellowing.

In general the oil-soluble xylenol resins formed from xylenol andaidehydes are readily soluble in caustic soda solution. This is not analtogether desirable feature. However, by heating the resin withglycerol (about 10 per cent) the resin is no longer soluble in dilute orconcentrated caustic soda solutions. A varnish made from theglycerol-treated resin and tung oil dries slightly faster than one madefrom untreated xylenol resin.

xylenol-formaldehyde resins, whether made from a two-step process ornot, have varying degrees of solubility in tung oil. Solubility dependsto some measure upon how far the reaction has been allowed to proceed,the proportions of the reactants and the type of catalyst used. Thus,many resins ,,made from xylenols and formaldehyde in the presence of anacid catalyst are insoluble in tung 011; others are partially solubleand still others are readily soluble. The resins described in the aboveexamples are entirely soluble. By heating a difilcultly soluble redcolor, but as heating progresses this color lightens to a pale brown.When all foaming ceases the resinis cooled down. At room temperature itis clear, hard, brittle and very readily soluble in tung 011.

Examipte 8.-The procedure of Example '7 may be varied by using themaleic acid as a reaction catalyst. 2 parts of'mixed commercialxylenols, or recovered xylenols, are mixed with 1 part of 37 per centaqueous formaldehyde and 2 per cent of maleic acid based on thexylenols. The mixture is refluxed until a well-defined resin layer formson the bottom of the reaction vessel, leaving a clear supernatant waterlayer. The water is then distilled off and the resin hardened by slowlyheating to 200-210 C. When cooled to room temperature, the resin islight in color, hard, brittle and very readily soluble in tung oil.

xylenol-formaldehyde products are resins which not only have theproperty of dissolving in tung oil, they also possess the property ofbeing solvents for tung oil and other drying oils. A composition thatcan be used as a shellac substitute may be made by dissolving smallamounts of tung oil in xylenol. resins.

Example 9.2 parts of an oil-soluble xylenolformaldehyderesin madeaccording to any of the foregoing examples are heated with 1 part oftung oil to 260-270 C. for about 15 minutes. The oil dissolves readilyin the molten resin to form a clear solution. When cooled to roomtemperature the resin is hard and brittle although it contains one-thirdoil. It may be dissolved in a suitable solvent such as alcohol andtoluol. A film dries lacquer-like, non-tacky and hard. It air-oxidizesin time so as tobecome insoluble.

Most of the xylenol-formaldehyde resins as described above are eitherinsoluble or diflicultly soluble in drying oils other than tung oil (inwhich they are readily soluble when made by the preferred procedure asabove outlined). Solu-' bility in drying oils is here meant solubilityin the proportions generally used in varnish making, whichproportions'may range from about part oil to 1 part resin (by weight)to, say, 4 parts oil to 1 part resin (or higher). This fact in itselfmay seem limiting; however, this is not the case, for any xylenol resinwhich is soluble in tung o-ilcan also be made readily soluble in linseedoil and other drying oils. The best method to eflect solution of axylenol-formaldehyde resin in linseed oil is, to first fuse the resinwith As stated tained from the lower-boiling fractions of cresylic acidare, in general, diflicultly soluble in drying oils. If, however, theyare. first fused with a modicum of tung oil, their solubility becomesexcellent by this treatment.

Example 10.-A- permanently fusible cresol resin is made by refluxingtogether 2 parts by weight of meta-para-cresol and 1 part by weight of37 per cent aqueous formaldehyde in the presence of 3 per cent of oxalicacid until a welldeflned supernatant water-layer appears. Refiuxing iscontinued for about 20 minutes after the water-layer appears. Thewater-layer is decanted and the resin is dehydrated byvacuumdistillation. Two parts by weight of this'resin are fused-with 1part of rawtung oil. The tem- 7s temperature the oil-modified resin islight 001- perature is taken to 230-250 C. and, when the oil hasdissolved completely in the resin and the mixture becomes clear, it iscooled to room temperature. The modified resin is light-colored, hard,brittle and very readily soluble in tung oil.

Example 11 .The xylenol-formaldehyde of Example 1 is insoluble inlinseed oil. However, a solution of the resin in the latter oil can bemade by first fusing the resin with linseed oil in the proportion of 2parts of resin to 1 part of linseed oil. The temperature is taken to280-290 C. until a clear melt results. When cooled to room ored, hard,brittle and very readily soluble in linseed, perilla, soya bean, or anyof the other drying or semi-drying oils.

In this last example any form of linseed oil may be. employed. Forinstance, raw linseed oil,

bodied or blown linseed, or mixtures of linseed with tung or otherdrying oils. Furthermore, other dryingoils may be employed in place oflinseed. They all yield resins substantially the same as regardssolubility, color, hardness, etc.

For the production of oil-soluble xylenol-formaldehyde resins theprocedure of Example 1 is preferably followed. A part of the xylenol maybe replaced by a small amount of other phenols such as phenol or cresoland oil-soluble resins result, but not if susbtantial proportions of thelower phenols are used. However, if larger amounts of such phenols areused and the resulting resins are worked up in accordance with themethods of Examples 10 and 11, completely oilsoluble resins result.Also, halogenated phenols such as p-chlorophenol may be co-condensedwith xylenol and formaldehyde to produce readily oil-soluble resins.Such compounds have the property of tempering the reaction betweencommercial mixed xylenols and formaldehyde.

Example 12.60 parts of commercial mixed xylenols and parts ofpara-chlorophenol are refluxed with 55 parts of 37 per cent aqueousformaldehyde containing 3 per cent of acetic acid for 2 hours. The speedof the reaction is cut down considerably by the presence of thechlorophenol. The supernatant water layer is decanted and the resindehydrated. Finally the resin is fused at a temperature of 200 C. Whencooled to room temperature the resin is of lightbrown color, hard,brittle and readily soluble in tung oil.

It has further been found that resins from halogenated xylenols possessgreat oil-solubility. Films of varnishes made from these resins arecharacterized by their light color when dry, that is, absence ofafter-yellowing. Such results may also be obtained by haiogenating theresin after it has been made. The varnishes made from these resins aresubstantially more fire-retardant and fireproof than varnishes made fromunhalogenated resins. In general, I prefer to carry out halogenationuntil about 0.75 to 1 atom of the halogen has combined with 1 moleculeof xylenol. The halogenation is usually carried out in the absence oflight or other halogenation catalyst. For instance, I may saturate waterwith chlorine gas and then agitate this solution with a small amount ofmixed xylenols in the dark. The reaction under such circumstances isalmost instantaneous. In general, the halogenated xylenols are dark incolor but may be lightened by distillation, preferably in the absence ofoxygen since they are somewhat oxidizable at high temperatures.

Halogenation of xylenols reduces the number of adehyde-reactivepositions in the molecule. Hence it produces a mixture of less reactivexylenols from the 'mixed commercial xylenols and resinification ofhalogenated xylenols and formaldehyde is comparable to resinification ofthe unreacted xylenols recovered by steam-distillation as in Example 1.

Example 13.-40 parts of oil-soluble xylenolformaldehyde resin madeaccording to Example 1 are dissolved in carbon tetrachloride and 2 to 3percent of iodine added. Chlorine gas is passed through the solutionuntil an amount equal to 1 atom of chlorine for each xylenol moleculehas been taken up, i. e., about 10 parts. The solvent is distilled off.The resulting resin is darker in color than the unchlorinated resin andis very,

readily oil-soluble.

Example 14.-164 parts of xylenols (boiling range 213-215 C.) are mixedwith 4 parts of anhydrous aluminum chloride and-chlorine gas is passedthrough the mixture in the absence of light until there is a gain of 30parts in weight. The xylenols are then washed repeatedly with slightlyalkaline water to free them from salts,.

acid and excess chlorine. The chlorinated xylenols, which are a darkpurple-red, are distilled and the fraction boiling between 213 and 230C. collected. One mole of this distillate is refluxed with 0.75 mole of3'7 per cent aqueous formaldehyde in the presence of 3 per cent ofoxalic acid as catalyst. The reaction proceeds slowly. After refluxingfor 2 hours the supernatant water is decanted and the liquid resinheated at atmospheric pressure to 120 C. to dehydrate it. Thetemperature is finally taken to 200 C. The resulting resin at roomtemperature is dark-colored, brittle and readily soluble in tung oil.

In general the varnishes produced with the resin described in Example 14are dark in color, drying to dark-colored films. However, by thefollowing procedure they may be made lightcoiored and the filmsextremely pale.

Example 15.One part by weight of the resin from Example 14 is heatedwith 2 parts by weight of raw tung oil to 260 C. and the temperatureheld at this point until the oil-resin mixture has become sufllcientlybodied. The varnish base at this stage is very dark colored. Five percent of lead naphthenate or litharge is then added. A precipitateimmediately forms with simultaneous lightening of the oil mixture to apale tan. As heating is continued this precipitate redissolves, theoil-base remaining very light colored. Finally 1 per cent of cobalt, or

- manganese drier is added and the varnish base cooled. When made into avarnish with suitable solvents, a film dries hard and colorless.

Although the use of xylenol resins in oil varnishes has been-stressed inthe foregoing, it has been found that other useful products can be,obtained by condensing mixed xylenols with formaldehyde in the presenceof a basic catalyst, then mixing such a resin with filler, tung oil, andso forth, and baking to an exceptionally hard cement-like mass.

Example 16.--One mole mixed commercial xylenols are refluxed with 2moles of aqueous formaldehyde in the presence of an alkaline cata lystsuch as sodium carbonate. The reaction is allowed to proceed just farenough so that a distinct clear supernatant water-layer is formed.

This water-layer is removed and the resin dehydrated by vacuum drying.This liquid resin is mixed with about 40 per cent of ground wood fillerand 10 to 20 per cent of tung oil. The mixture is of a putty consistencyand in that form may be pressed into molds and baked in an oven at'about90 C. to a hard product.

Example 17.--3 parts of commercial mixed xylenols or recovered xylenolsare heated with 4 parts of 3'7 per cent aqueous formaldehyde and about 1per cent of caustic soda to just below boiling temperature for 1 hour.The supernatant water is poured ofi andthe liquid resin dehydrated. Whenin the form of a slightly viscous liquid at room temperature it is mixedwith enough raw Turkey umber or iron oxide to bring it to a putty-likeconsistency. About 5 per cent of hexamethylenetetramine is mixed in themass and it is cast into forms. By baking it at 75 C. for from 48 to 100hours a solid, homogeneous product is obtained which is exceedinglystrong. Tung oil may be dissolved in the resin to give it additionaltoughness.

What I claim is:

1. The process of forming an oil-soluble xyleof about 1 mole offormaldehyde to 1 mole of xylenols,'and mixing the resin from the secondreaction with the resin from the first reaction.

2. The process of producing condensation products which comprisesreacting a mixture of xylenols with formaldehyde insumcient to givecondensation products with all of the xylenols, separating unreactedxylenol and reacting the latter with formaldehyde to give an oil-solublecondensation product.

3. The process of producing condensation products which compriseshalogenating a condensation product of formaldehyde and a xylenol.

CARLETON ELLIS.

